create soft link with template

Add the the function softlink to the template rendering, so that
{{ softlink: "/bin/bash" }} for the file `/bin/run.ww` will create
a soft link to `/bin/bash`
It's also possible to "import" soft links from the host, e.g. the
template
{{ ImportLink "/etc/localtime" }}
set the timezone from the host

Signed-off-by: Christian Goll <cgoll@suse.com>

internal/pkg/overlay/funcmap.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"path"
+	"path/filepath"
 	"strings"
 
 	warewulfconf "github.com/warewulf/warewulf/internal/pkg/config"
@@ -122,3 +123,12 @@ func createIgnitionJson(node *node.Node) string {
 	tmpYaml, _ := json.Marshal(&conf)
 	return string(tmpYaml)
 }
+
+func importSoftlink(lnk string) string {
+	path, err := filepath.EvalSymlinks(lnk)
+	if err != nil {
+		return "abort"
+	}
+	wwlog.Debug("importing softlink pointing to: %s", path)
+	return fmt.Sprintf("{{ /* softlink \"%s\" */ }}", path)
+}

internal/pkg/overlay/overlay.go

@@ -238,12 +238,17 @@ func BuildOverlayIndir(nodeData node.Node, overlayNames []string, outputDir stri
 					// search for magic file name comment
 					fileScanner := bufio.NewScanner(bytes.NewReader(buffer.Bytes()))
 					fileScanner.Split(ScanLines)
-					reg := regexp.MustCompile(`.*{{\s*/\*\s*file\s*["'](.*)["']\s*\*/\s*}}.*`)
+					regFile := regexp.MustCompile(`.*{{\s*/\*\s*file\s*["'](.*)["']\s*\*/\s*}}.*`)
+					regLink := regexp.MustCompile(`.*{{\s*/\*\s*softlink\s*["'](.*)["']\s*\*/\s*}}.*`)
 					foundFileComment := false
 					for fileScanner.Scan() {
 						line := fileScanner.Text()
-						filenameFromTemplate := reg.FindAllStringSubmatch(line, -1)
+						filenameFromTemplate := regFile.FindAllStringSubmatch(line, -1)
-						if len(filenameFromTemplate) != 0 {
+						softlinkFromTemplate := regLink.FindAllStringSubmatch(line, -1)
+						if len(softlinkFromTemplate) != 0 {
+							wwlog.Debug("Creating soft link %s -> %s", destFileName, softlinkFromTemplate[0][1])
+							return os.Symlink(softlinkFromTemplate[0][1], path.Join(outputDir, destFileName))
+						} else if len(filenameFromTemplate) != 0 {
 							wwlog.Debug("Found multiple comment, new filename %s", filenameFromTemplate[0][1])
 							if foundFileComment {
 								err = CarefulWriteBuffer(path.Join(outputDir, destFileName),
@@ -371,10 +376,12 @@ func RenderTemplateFile(fileName string, data TemplateStruct) (
 		"Include":      templateFileInclude,
 		"IncludeFrom":  templateContainerFileInclude,
 		"IncludeBlock": templateFileBlock,
+		"ImportLink":   importSoftlink,
 		"basename":     path.Base,
 		"inc":          func(i int) int { return i + 1 },
 		"dec":          func(i int) int { return i - 1 },
 		"file":         func(str string) string { return fmt.Sprintf("{{ /* file \"%s\" */ }}", str) },
+		"softlink":     func(str string) string { return fmt.Sprintf("{{ /* softlink \"%s\" */ }}", str) },
 		"IgnitionJson": func() string {
 			str := createIgnitionJson(data.ThisNode)
 			if str != "" {